Hey I recognize that terrible sound!
Slow Motion Footage Of Apple Watch Ejecting Water From Speaker

This is a video of Gavin from The Slow Mo Guys (where’s Dan — what did you do to him?!) capturing some footage of an Apple Watch ejecting water from its speaker at approximately 196Hz when Water Lock is turned off. Me? I never remember to turn Water Lock on in the first place, which may explain why my Apple Watch doesn’t work anymore. “That’s a slap bracelet.” And that may explain it even better. Hold out your arm!

Thanks to Charlie H, who agrees this is the technological equivalent of turning your head sideways and banging on it after getting out of a pool.